The present invention is directed to a polymeric composition to be used in producing foam. Specifically, the polymeric composition is comprised of a high density polyethylene, an alkenyl aromatic polymer and a linear low density polyethylene.
Low density polymeric foams, which have a density in the range of 10 kg/m3 to 160 kg/m3, have been made for many years. These polymeric foams have generally been made by combining a physical blowing agent with a molten polymeric mixture under pressure and, after thorough mixing, extruding the combination through an appropriate die into a lower pressure atmosphere.
Polymeric foams designed for protective packaging of books, furniture, office equipment, weapons, and other items of value require light weight, resilient materials in order to protect the packaged items from handling without adding significant weight and bulk, and thus cost, to the overall package for transport. Polymeric foams designed for applications such as recreational items like bodyboards and floatation devices also require resilient materials so as not to permanently deform under multiple applications of compressive and shear forces during use. Polymeric foams designed for floor underlayment also require resilient materials so as not to permanently deform under multiple applications of compressive forces during use. Although there have been recent reports of compositions comprising other polymers for foams made for such applications, resilient, low-density polymeric foams are most commonly made from low density polyethylene (LDPE).
Polymeric foams composed of LDPE are generally considered to be resilient and non-brittle, which are desirable properties. However, despite widespread usage, these foams have disadvantages related directly to the LDPE component. Because LDPE will reduce important physical properties of blends that comprise the more widely-used polyethylenes, “high density polyethylene” and “linear low density polyethylene”, there are limited recovery or reuse options for the LDPE packaging material after the packaged item is delivered to the end-user. Consequently, the major fraction of LDPE-only materials used for packaging is destroyed by incineration or is deposited in landfills. Another disadvantage is that LDPE is not a commodity and therefore poses higher material costs than related commodity plastics like high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). HDPE has extensive usage in many applications such as bottles for freshly packaged liquids for human consumption like milk, orange juice, and ciders, bottles for household and industrial chemicals, flexible tubing, and toys. LLDPE has widespread usage for packaging films, plastic wraps, and plastic bags. Furthermore, the current process requirements for LDPE foams severely restrict the incorporation of recycled polyethylene from post-consumer and post-industrial sources. Incorporation of recycled polyethylene into a polyethylene foam structure would be very desirable as new regulations are introduced to reduce waste and to recover and reuse industrial materials.
Accordingly, a need exists for foams that overcome the above-noted shortcomings associated with LDPE-only foams.